Various compressive devices for a multitude of medical uses have been present for many years. The benefit is indicated for several medical problems. The most common, and most threatening, is in the prevention of pulmonary embolism from deep vein thrombosis of the great veins of the legs. Compressive devices have been used for treatment of both venous insufficiency in upper and lower extremities and for the treatment of lymphedema in a limb whose lymph drainage channels have been interrupted by surgery or radiation.
A constant danger to an immobilized patient is the tendency to develop thrombophlebitis with formation of intravascular thrombi which may detach and flow towards the heart and lungs resulting in a pulmonary embolus which may prove fatal. With immobility, the flow of blood in the venous side of the circulatory system is reduced to a point favoring venous stasis and subsequent localized clot formation. Proximal to the adherent clot, the blood in the vein is less adherent to the vessel wall. It is usually this portion of the clot which detaches itself and acts as an embolus to the heart and lungs.
There are many situations in a hospital population where the above pertains, such as the patient who has recently suffered a heart attack, the patient in coma, the patient with a fracture, the post-operative patient who cannot be ambulated, and the burn patient. A potential danger is also during prolonged surgical procedures with the patient completely anesthetized. At present, the only methods to prevent thrombophlebitis with resultant thrombus formation are early ambulation, application of elastic hose and anticoagulant therapy (heparin, coumadin, warfarin sodium, and phenindione). Early ambulation is contraindicated in such patients who have suffered an acute myocardial infarction or fractured hip. Anticoagulants may produce bleeding especially in an early post-operative patient. The elastic hose merely constricts the musculature of the lower extremity but does not mimic the pulsatile milking action of leg muscles upon the veins which enhance venous blood flow back to the heart. It has been the practice in extreme cases, in order to increase blood supply to a local area blocked by an obstruction, to surgically remove the lesion from the artery. When there is severely diminished blood flow through the extremity, ulceration or gangrene may develop and lead to amputation.
In those cases where it is not feasible to administer anticoagulant treatment and surgery is not required, other therapy has been pursued for the purpose of increasing blood circulation through the lower extremities. In the treatment of middle-aged and elderly bedfast patients, it is a well known practice to increase the rate of blood circulation through the lower extremities by constricting the extremities through the use of elastic stockings to prevent thrombus formation. Correctly applied elastic bandages may be used in place of elastic stockings by removing and re-applying them every eight hours, checking the legs for redness, swelling and tenderness.
When there has been destruction of the valves of the deep veins within the lower extremity, a pneumatic legging may be prescribed. The legging is zippered on the patient's leg and has a cloth cover and a rubber bladder inside into which air is pumped to a pressure of 30 mm. Hg. A rhythmic increase in pressure in the veins results as the patient walks. The device is intended for use in cases where the person is fully ambulatory and edema or swelling of the lower extremities is to be prevented. If the patient is unable to walk and is immobilized, no increase in pressure in the veins will occur as the extremity muscles are not stimulated. There is need for a pressure control device to be fitted on the extremity of an immobilized patient to aid in the venous return of blood to the heart for the prevention of thrombus formation.
Additionally, there are devices currently being studied for treatment of angina pectoris by external venous compression, which is performed in sequential sessions over a period of weeks and months.
The devices in use now are crude systems which utilize external compression by either pneumatic or fluid compressive devices wrapped around the limbs. They are all encumbered by the need to attach these to a central console which provides the force of compression through tubes connected to the compression devices. These consoles are normally bulky, frequently noisy and commit the patient to bed rest while in use.
Accordingly, there is need to provide a sequential application of compressive forces for squeezing or constricting the muscles thereof to prevent stasis of blood with resultant thrombus formation in the leg veins and pulmonary emboli associated therewith. Additionally, what is needed are devices for applying compressive forces which are easy to place around the portion of the body which may be subject to thrombophlebitis or venous thrombosis. These devices should also be able to selectively apply the compressive force to allow the device to stimulate fluid flow to and from the portion of the body to be treated.